Portland cement is one of the most widely used materials in the construction industry. Although unmodified concrete and cement mortar systems (i.e., those not containing a polymer latex modifier) have adequate properties for many construction applications, there remain many areas in which such properties, particularly strength properties, are not acceptable.
Latex-modified portland cement systems have been developed that significantly change the physical properties of unmodified concrete and cement mortar. Of such latex-modified cement systems, the addition of styrene-butadiene polymer latexes to portland cement have provided compositions having improved strength, flexibility, adhesion, elongation at break, as well as smaller volume change. U.S. Pat. No. 3,043,790 (Re 28,722) and U.S. Pat. No. 3,895,953 are directed to such latex-modified portland cement systems.
The present invention is directed to a cement additive based on a styrene-butadiene-acrylonitrile interpolymer latex, a nonionic surfactant, an anionic surfactant and a polyorganosiloxane foam depressant, and to cement compositions containing the same, having significantly improved strength properties.